Design of a test bench for the flow ripple determination in positive-displacement hydraulic pumps

This thesis is about the study of two important characteristic values of positive-displacement pumps, the source flow ripple, and the source impedance. The first one represents the flow fluctuations generated inside the pump, while the other one the complex ratio between the pressure fluctuation and the flow ripple occurring at the outlet port of the pump when the Norton model is used. The fluctuations of flow rate are inherent to these types of machines due to their working principle. Moreover, they generate pressure fluctuations in the hydraulic circuit at which the pump is connected and consequently leading to fluid-born noises. By knowing the two mentioned features values and the ripple propagation characteristics of the circuit’s components, is possible then to compute the pressure fluctuations through mathematical models. In such a way, is furnished the tool to design circuits with low hydraulic noises values. The main aims of this thesis are the following ones: •??Design a test bench suitable for characterizing pumps of different sizes using three different kits. •??Write a Matlab code to compute the source flow ripple and the source impedance of positive-displacement pumps. •??Test a 10.6 cc/rev external gears pump to prove the correctness of the code and of the methodology followed. For both the design of the test bench and the drafting of the code is followed the standard ISO 10767:1-2015. To design the three kits are taken into account two external gear pumps and an axial piston pump equivalent to SAE-A, SAE-B and SAE-C dimensions according to standard SAE J-744. In this way is possible to cover a wide range of pump dimensions. The Matlab code provides a tool not only for the computation of the characteristic values of the pump but also for a direct verification of the calculations through different mathematical models. Moreover, for the verification of the methodology, the 10.6 cc/rev pump is tested in the Laboratory of Fluid Mechanics of the “Universidad Politécnica de Cataluña”. Here, after analyzing the pump’s dimensions, the required test bench is mounted and different tests are carried out. The experimental results achieved show the typical behaviour of an external gear pump. In addition, they exhibit a good correlation with both mathematical models and scientific articles, validating our calculations. To sum up, this thesis gives a useful overview of the pump’s main characteristics and allows to follow a methodology regarding the design of a test bench suitable to characterize positive-displacement pumps having different dimensions.